For the study, researchers followed 1,742 patients with IBD and a control group of 17,420 individuals for up to 16 years, starting when they were 61 years old on average and free of dementia. By the end of the study, 5.5 percent of people with IBD and 1.4 percent of individuals in the control group developed dementia. In addition, people with IBD developed dementia roughly seven years earlier than individuals without IBD, at an average age of 76 and 83, respectively. “IBD was not previously known to be associated with dementia risk,” says the study coauthor Hohui Wang, MD, an assistant clinical professor of psychiatry at the University of California in San Francisco.
Chronic Inflammation and Dementia Risk
Chronic inflammation in the digestive tract is a hallmark of IBD, which includes conditions like ulcerative colitis and Crohn’s disease. While inflammation can trigger symptoms like abdominal pain, bloody stools, and diarrhea when IBD is active, the inflammation can be present even when people with IBD are in clinical remission and symptom-free, the study team writes. One study, published in August 2018 in Neurobiology of Aging, found that systemic inflammation in middle age was associated with structural abnormalities in white matter in the brain among older adults. Changes in white matter in the brain are linked to cognitive decline and dementia. Another study, published in March 2019 in Neurology, followed more than 12,000 people for 20 years starting when they were 57 years old on average. People who had the highest levels of so-called C-reactive protein, a marker of systemic inflammation, in their blood at the start of the study experienced far steeper cognitive decline during the study than people with the lowest levels of C-reactive protein. A study published in May 2017 in the Journal of Epidemiology and Community Health examined the dementia risk associated with several autoimmune diseases, including psoriasis, lupus, and multiple sclerosis that, like IBD, are thought to involve systemic inflammation. Compared with individuals without autoimmune disorders, people with psoriasis were 29 percent more likely to develop dementia, while lupus was tied to a 46 percent higher dementia risk, and multiple sclerosis was associated with a 97 percent greater chance of dementia.
Inflammation and Changes in the Brain
These previous studies suggest that systemic inflammation might trigger neuroinflammatory changes in the brain, says the lead study author, Bing Zhang, MD, a clinical fellow in gastroenterology at the University of California in San Francisco. While the current study finds an association between IBD and dementia, it wasn’t designed to prove whether IBD directly causes cognitive decline or dementia, says Dr. Zhang. In the current study, researchers didn’t find a meaningful difference in dementia risk based on what type of IBD people had. The dementia risk was similar for ulcerative colitis and for Crohn’s disease.
Limitations of the Study
One limitation of the study is that researchers were unable to assess whether individual IBD medications or surgical treatments for IBD might impact dementia risk. Researchers also lacked data on lifestyle factors like diet and exercise habits, which could both independently influence dementia risk. Adopting healthy eating and exercise habits, not smoking, drinking alcohol in moderation, managing stress, and getting enough sleep are all lifestyle factors that may impact the risk of dementia, says Miguel Regueiro, MD, the chair of the department of gastroenterology, hepatology, and nutrition at the Cleveland Clinic in Ohio. “These lifestyle factors may have a higher association with … dementia than just the IBD,” says Dr. Regueiro, who wasn’t involved in the study. RELATED: Exercise, Eat Right, Socialize, and Keep Learning to Prevent Dementia
